Trying to cross-ref some old-school steering parts
 

I'm trying to find out what parts were used to cobble together my steering, and looking to see if y'all can help. The stock RX-2 tie rod ends, idler and pitman arm all use smaller tapered shanks at their joints than FB RX-7. I've got a reamed center link and steering knuckles, so that they accept RX-7 hardware instead. The problem, however, is with the pitman. The pitman that's on my car has a large shank, ala RX-7, but the splines on the end are smaller than a 7's steering box. The splines are the same size as what's on my existing (and new) steering box.

Did Mazda step up the size of its tapers before the RX-7, but stuck with the smaller splines? I'm trying to figure out where my pitman came from and how to best replace it.